This invention is directed to a grinding machine and particularly to a grinding machine used to grind a flat surface to extremely close tolerance parallel to another surface on a concrete or stone block member.
In the kind of grinding machine to which this invention relates, a grinder is incorporated. There are several commercially available grinders that are constructed with precision spindles and capable of extremely accurate surface grinding. These grinders incorporate grinding wheels designed to grind on the cylindrical surface or on the flat face of the wheel. Typically, the objective is to grind a perfectly flat surface or an object. To grind the entire surface of an object, the grinding wheel is moved relative to the object. This may be accomplished by moving the grinding wheel or by moving the object and holding the grinder stationary. In order to maintain a precisely flat ground surface within close tolerances, it is necessary that the moving part, either the grinder or the block to be ground, be moved in a precisely defined plane.
The known grinding machines accomplish relative movement between the object and the grinder on three dimensional axes. However, these known grinding machines have not achieved sufficient accuracy in maintaining this relative movement within a precise plane. Typically, in order to achieve a flat ground surface, the area of contact with the grinding wheel is reduced, such as to a line of contact between the object and the cylindrical surface of the grinding wheel. This approach greatly increases grinding time and is too expensive for many applications, such as the grinding of concrete or stone modular blocks.
Modular blocks are examples of products on which these grinding machines are used. Such modular blocks are cast of concrete and are adapted for assembly in face-toface relationship such that, when held together by tension rods, the modular block assembly forms a structural member such as a beam or a column. Examples of some of these modular blocks are described and illustrated in Azimi U. S. Pat. No. 4,694,629. The contacting faces of these modular blocks must be flat within extremely close tolerances and must be exactly parallel so that they fit tightly and accurately together across the entire contacting faces so that forces and loads will be transferred uniformly from one block to another.
In the casting of these modular blocks, the mold has precisely formed surfaces, but the faces of a molded block are not flat within the required 0.0005 inch tolerance. Therefore, it is necessary that these faces be ac curately ground by a grinding machine. However, no grinding machine has been developed heretofore that compensates for wear on the grinding surface of the grinding wheel while accurately supporting a concrete or stone block to achieve a ground surface within the desired tolerances of no more than 0.0005 inch and do so within an acceptable period of time.
Therefore, the general object of this invention is to provide a grinding machine that is of rigid structural construction, that has an accurately supported truck movable to move a block to be ground relative to the grinding wheel, and that has precisely controlled adjusting means for accurately establishing the path of movement of the truck so that the surface to be ground is set in precisely the desired plane.